compilerplugins/clang/faileddyncast.cxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  */
   9
  10 #include <algorithm>
  11
  12 #include "clang/AST/Attr.h"
  13 #include "clang/AST/CXXInheritance.h"
  14
  15 #include "plugin.hxx"
  16
  17 namespace {
  18
  19 // cf. Clang's clang::AST::CXXDynamicCastExpr::isAlwaysNull
  20 // (lib/AST/ExprCXX.cpp):
  21 bool isAlwaysNull(CXXDynamicCastExpr const * expr) {
  22   QualType SrcType = expr->getSubExpr()->getType();
  23   QualType DestType = expr->getType();
  24
  25   if (const clang::PointerType *SrcPTy = SrcType->getAs<clang::PointerType>()) {
  26     SrcType = SrcPTy->getPointeeType();
  27 #if 0
  28     DestType = DestType->castAs<PointerType>()->getPointeeType();
  29 #else
  30     auto DstPTy = DestType->getAs<clang::PointerType>();
  31     if (!DstPTy)
  32       return false;
  33     DestType = DstPTy->getPointeeType();
  34 #endif
  35   }
  36
  37   if (DestType->isVoidType())
  38     return false;
  39
  40 #if 0
  41   const CXXRecordDecl *SrcRD =
  42     cast<CXXRecordDecl>(SrcType->castAs<RecordType>()->getDecl());
  43 #else
  44   auto SrcRT = SrcType->getAs<RecordType>();
  45   if (!SrcRT)
  46     return false;
  47   const CXXRecordDecl *SrcRD = cast<CXXRecordDecl>(SrcRT->getDecl());
  48 #endif
  49
  50 #if 0
  51   if (!SrcRD->hasAttr<FinalAttr>())
  52     return false;
  53 #endif
  54
  55 #if 0
  56   const CXXRecordDecl *DestRD =
  57     cast<CXXRecordDecl>(DestType->castAs<RecordType>()->getDecl());
  58 #else
  59   auto DestRT = DestType->getAs<RecordType>();
  60   if (!DestRT)
  61     return false;
  62   const CXXRecordDecl *DestRD = cast<CXXRecordDecl>(DestRT->getDecl());
  63 #endif
  64
  65 #if 1
  66   if (!(SrcRD && DestRD))
  67     return false;
  68
  69   if (DestRD->hasAttr<FinalAttr>()) {
  70     CXXBasePaths Paths(/*FindAmbiguities=*/false, /*RecordPaths=*/true,
  71                        /*DetectVirtual=*/false);
  72     if (DestRD->isDerivedFrom(SrcRD, Paths) &&
  73         std::all_of(Paths.begin(), Paths.end(),
  74                     [](CXXBasePath const & Path) {
  75                         return Path.Access != AS_public; }))
  76       return true;
  77   }
  78
  79   if (!SrcRD->hasAttr<FinalAttr>())
  80     return false;
  81 #endif
  82
  83 #if 0
  84   return !DestRD->isDerivedFrom(SrcRD);
  85 #else
  86   return !(DestRD->isDerivedFrom(SrcRD)
  87            || SrcRD->isDerivedFrom(DestRD)
  88            || SrcRD == DestRD);
  89 #endif
  90 }
  91
  92 class FailedDynCast:
  93     public RecursiveASTVisitor<FailedDynCast>, public loplugin::Plugin
  94 {
  95 public:
  96     explicit FailedDynCast(loplugin::InstantiationData const & data):
  97         Plugin(data) {}
  98
  99     bool shouldVisitTemplateInstantiations() const { return true; }
 100
 101     void run() override;
 102
 103     bool VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr);
 104 };
 105
 106 void FailedDynCast::run() {
 107     if (compiler.getLangOpts().CPlusPlus) {
 108         TraverseDecl(compiler.getASTContext().getTranslationUnitDecl());
 109     }
 110 }
 111
 112 bool FailedDynCast::VisitCXXDynamicCastExpr(CXXDynamicCastExpr const * expr) {
 113     if (ignoreLocation(expr)) {
 114         return true;
 115     }
 116     if (isAlwaysNull(expr)) {
 117         report(
 118             DiagnosticsEngine::Warning,
 119             "dynamic_cast from %0 to %1 always fails", expr->getLocStart())
 120             << expr->getSubExpr()->getType() << expr->getType()
 121             << expr->getSourceRange();
 122     }
 123     return true;
 124 }
 125
 126 loplugin::Plugin::Registration<FailedDynCast> X("faileddyncast");
 127
 128 }
 129
 130 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */